The present invention relates to a printhead carriage including a body that is guided and driven for reciprocating movement in a printer, a mounting plate for a printhead assembly, and a suspension structure adjustably connecting the mounting plate to the body, the suspension structure comprising a framework of hinge plates having elastic hinges that are formed by reduced-width portions of the hinge plates and at least one adjusting mechanism adapted to adjust the position of the mounting plate by elastically deflecting at least one of the hinges.
In a scanning-type printer, e.g. an ink jet printer, a printhead carriage is moved back and forth in a main scanning direction Y, so as to scan a recording medium that is advanced step-wise in a sub-scanning direction X over a print surface. For obtaining a good print quality, it is important that the mounting plate which carries the printheads is exactly adjusted relative to the print surface. For example, in an ink jet printer, the printheads comprise one or more arrays of nozzles from which ink droplets are ejected onto the recording medium at appropriate moments during the scan movement of the carriage, so that an image is formed on the recording medium. Accordingly, the mounting plate must be adjusted so that the flight distance of the ink droplets is identical for all nozzles. This means that the mounting plate should be held in a stable position so that it is exactly parallel to the print surface. Moreover, the angle of the nozzle array or arrays relative to the main scanning direction must be adjusted with a high degree of accuracy, e.g., to 90°.
If the carriage carries a plurality of printheads, as is the case for example in a multi-color printer, another problem may arise from the fact that the operation of the printheads is frequently accompanied by the generation of a considerable amount of heat, so that the mounting plate is subject to thermal expansion which may change the positions of the printheads relative to one another. This is particularly the case for a hot melt ink jet printer which operates with ink that is solid at room temperature, so that the printheads must be heated to a relatively high temperature, for example, 100° C. or more, in order to melt the ink. If the temperature of the mounting plate is uniform, the thermal expansion may be compensated for by appropriately controlling the timing at which the individual nozzles are energized. However, if the temperature distribution of the mounting plate is not uniform, it becomes difficult to compensate for the thermal expansion.
In order to achieve a high productivity of the printer, the carriage must be accelerated and decelerated at the beginning and at the end of each scan pass with a considerably high rate. As a result, considerable forces of inertia are generated which may cause the mounting plate to shift or to vibrate. It is therefore required that the suspension structure has a sufficient stiffness for stably holding the mounting plate in the desired position.